Prolonged allergen exposure induces structural airway changes in sensitized rats

The integrin receptor beta7 subunit mediates airway remodeling and hyperresponsiveness in allergen exposed mice

BACKGROUND

Fibroblast differentiation to a myofibroblast phenotype is a feature of airway remodeling in asthma. Lung fibroblasts express the integrin receptor α4β7 and fibronectin induces myofibroblast differentiation via this receptor.

OBJECTIVES

To investigate the role of the β7 integrin receptor subunit and α4β7 integrin complex in airway remodeling and airway hyperresponsiveness (AHR) in a murine model of chronic allergen exposure.

METHODS

C57BL/6 wild type (WT) and β7 integrin null mice (β7 -/-) were sensitized (days 1,10) and challenged with ovalbumin (OVA) three times a week for one or 4 weeks. Similar experiments were performed with WT mice in the presence or absence of α4β7 blocking antibodies. Bronchoalveolar (BAL) cell counts, AHR, histological evaluation, soluble collagen content, Transforming growth factor-β (TGFβ) and Interleukin-13 (IL13) were measured. Phenotype of fibroblasts cultured from WT and β7 -/- saline (SAL) and OVA treated mice was evaluated.

RESULTS

Eosinophil numbers were similar in WT vs β7-/- mice. Prolonged OVA exposure in β7-/- mice was associated with reduced AHR, lung collagen content, peribronchial smooth muscle, lung tissue TGFβ and IL13 expression as compared to WT. Similar findings were observed in WT mice treated with α4β7 blocking antibodies. Fibroblast migration was enhanced in response to OVA in WT but not β7 -/- fibroblasts. α-SMA and fibronectin expression were reduced in β7-/- fibroblasts relative to WT.

CONCLUSIONS

The β7 integrin subunit and the α4β7 integrin complex modulate AHR and airway remodeling in a murine model of allergen exposure. This effect is, at least in part, explained by inhibition of fibroblast activation and is independent of eosinophilic inflammation.

Fine particulate matter contributes to COPD-like pathophysiology: experimental evidence from rats exposed to diesel exhaust particles

BACKGROUND

Ambient fine particulate matter (PM2.5) is considered a plausible contributor to the onset of chronic obstructive pulmonary disease (COPD). Mechanistic studies are needed to augment the causality of epidemiologic findings. In this study, we aimed to test the hypothesis that repeated exposure to diesel exhaust particles (DEP), a model PM2.5, causes COPD-like pathophysiologic alterations, consequently leading to the development of specific disease phenotypes. Sprague Dawley rats, representing healthy lungs, were randomly assigned to inhale filtered clean air or DEP at a steady-state concentration of 1.03 mg/m3 (mass concentration), 4 h per day, consecutively for 2, 4, and 8 weeks, respectively. Pulmonary inflammation, morphologies and function were examined.

RESULTS

Black carbon (a component of DEP) loading in bronchoalveolar lavage macrophages demonstrated a dose-dependent increase in rats following DEP exposures of different durations, indicating that DEP deposited and accumulated in the peripheral lung. Total wall areas (WAt) of small airways, but not of large airways, were significantly increased following DEP exposures, compared to those following filtered air exposures. Consistently, the expression of α-smooth muscle actin (α-SMA) in peripheral lung was elevated following DEP exposures. Fibrosis areas surrounding the small airways and content of hydroxyproline in lung tissue increased significantly following 4-week and 8-week DEP exposure as compared to the filtered air controls. In addition, goblet cell hyperplasia and mucus hypersecretions were evident in small airways following 4-week and 8-week DEP exposures. Lung resistance and total lung capacity were significantly increased following DEP exposures. Serum levels of two oxidative stress biomarkers (MDA and 8-OHdG) were significantly increased. A dramatical recruitment of eosinophils (14.0-fold increase over the control) and macrophages (3.2-fold increase) to the submucosa area of small airways was observed following DEP exposures.

CONCLUSIONS

DEP exposures over the courses of 2 to 8 weeks induced COPD-like pathophysiology in rats, with characteristic small airway remodeling, mucus hypersecretion, and eosinophilic inflammation. The results provide insights on the pathophysiologic mechanisms by which PM2.5 exposures cause COPD especially the eosinophilic phenotype.

Similarities and differences in kinetic characteristics of airways inflammation, formation of inducible bronchial-associated lymphoid tissue and remodeling between young and old murine asthma surrogates induced with house dust mite

Elderly asthmatics have higher morbidity and mortality compared with those of youngers. It has been shown that there are also some differences in clinic phenomena between young and elderly asthmatics, however, there is lack of the kinetic comparisons of the changes in the development of asthma between two populations. To better understand the specific pathophysiological manifestations in older patients with asthma, we dynamically and parallelly compared pathophysiological changes in the airways and lung tissues between young and old murine asthma surrogates based on sensitization and challenge with house dust mite (HDM). Murine models were established in young (6-8-week-old) and old (16-17-month-old) female wild-type C57BL/6 mice. Our data showed that repetitive HDM exposure induced relatively low type 2 immune responses (airway hyperresponsiveness, eosinophils recruitment, expression of type 2 cytokines, mucus secretion, serum HDM specific immunoglobulin E (IgE) and IgG) in old mice. However, the type 3 immune responses (neutrophils infiltration and IL-17A expression) were enhanced in old HDM exposed mice, which sustained longer and higher than that of young mice. Notably, the relatively weakened allergic inflammation characteristics might be associated with lower numbers of CD20⁺ B cells and IgE⁺ cells in the iBALTs in old mice compared with those in young mice. Our data suggest that aging might compromise the ability to induce type 2 immune responses, but enhance type 3 immune responses upon repetitive HDM challenge, which might cause relevant phenomena in old experimental mice and might even be applicable to elderly patients with asthma in the clinic.

Investigation of the Relationship Between Trefoil Factor Family Peptides and Sinonasal Inflammation

The trefoil factor family (TFF) is a relatively new family of peptides. In some studies, an association between trefoil factors and inflammatory diseases of the nasal and paranasal sinuses has been suggested. However, it is still not clear whether there is a relationship between trefoil peptides and inflammation of the respiratory tract. The aims of this study are to determine the presence of TFF1, TFF2, and TFF3 in the nasal mucosa and investigate their relationships with inflammation by using rat models of various sinonasal inflammations. Nasal tampon, lipopolysaccharide, and ovalbumin were used to generate rat models of sinonasal inflammation, i.e., rhinosinusitis and allergic rhinitis. The study was conducted on seventy rats in seven groups, each with ten rats: four groups with rhinosinusitis, two groups with allergic rhinitis, and a control group. Histological evaluation of sinonasal mucosa from all rats was performed, and Trefoil factors were investigated using immunohistochemical methods. All three TFF peptides were detected in rat nasal mucosa by histological evaluation. No significant differences in the trefoil factor scores were observed among the study groups. A significant correlation between the TFF1 and TFF3 scores and loss of cilia was identified (p < 0.05). In conclusion, no direct relationship between sinonasal inflammation and TFF scores was observed. However, a possible association between the TFF and epithelial damage or regeneration in sinonasal inflammation can be suggested based on the correlation observed between the TFF1 and TFF3 scores and scores of cilia loss.

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

Azithromycin induces apoptosis in airway smooth muscle cells through mitochondrial pathway in a rat asthma model

Background

The proliferation of airway smooth muscle cells (ASMCs) is a key feature of airway remodeling in asthma. Azithromycin (AZM) has been shown to decrease bronchial hyperresponsiveness and airway inflammation in asthmatics; however, the role of AZM in ASMC proliferation remains unclear. Thus, we investigated the effect of AZM on ASMC proliferation in a rat model of experimental asthma.

Methods

We isolated ASMCs from rats sensitized and challenged by ovabulmin (OVA), and then treated with different concentrations of AZM. Cytotoxicity of ASMC was evaluated by Cell Counting Kit-8 (CCK-8) assay, morphological change was examined with laser confocal microscope after Annexin V/propidium iodide (PI) double staining, mitochondrial membrane potential was determined with JC-1 staining, and the expression of cytochrome C was examined by western blot.

Results

The relative surface areas of airway wall and smooth muscle layers in OVA-sensitized rats were significantly increased compared to those in the control group. Furthermore, in OVA-sensitized rats, the mitochondrial membrane potential of ASMC was higher, while the expression of mitochondria cytochrome C was lower compared to that in control rats. After AZM treatment, ASMC apoptosis was increased, mitochondrial membrane potential reduced, and the protein level of cytosolic cytochrome C was increased.

Conclusions

This study demonstrated that AZM increased the apoptosis of ASMCs through a mitochondrial pathway, which might play an important role in ASMs proliferation during asthmatic remodeling.

Structure-Activity Relationship Analysis of Psychedelics in a Rat Model of Asthma Reveals the Anti-Inflammatory Pharmacophore

Psychedelic drugs can exert potent anti-inflammatory effects. However, anti-inflammatory effects do not appear to correlate with behavioral activity, suggesting different underlying mechanisms. We hypothesized that the distinct structural features of psychedelics underlie functionally selective mechanisms at the target 5-HT2A receptor to elicit maximal anti-inflammatory effects. In order to test this hypothesis, we developed a new rat-based screening platform for allergic asthma. Next, we investigated 21 agonists at the 5-HT2A receptor from the three primary chemotypes (phenylalkylamine, ergoline, and tryptamine) for their ability to prevent airways hyperresponsiveness as a measure of pulmonary inflammation. Furthermore, we assessed each drug for in vitro activation of the canonical signaling pathway, calcium mobilization, from the 5-HT2A receptor. We find that the drug 2,5-dimethoxyphenethylamine (2C-H) represents the pharmacophore for anti-inflammatory activity and identify structural modifications that are either permissive or detrimental to anti-inflammatory activity. Additionally, there is no correlation between the ability of a particular psychedelic to activate intracellular calcium mobilization and to prevent the symptoms of asthma or with behavioral potencies. Our results support the notions that specific structural features mediate functional selectivity underlying anti-inflammatory activity and that relevant receptor activated pathways necessary for anti-inflammatory activity are different from canonical signaling pathways. Our results inform on the nature of interactions between ligands at the 5-HT2A receptor as they relate to anti-inflammatory activity and are crucial for the development of new 5-HT2A receptor agonists for anti-inflammatory therapeutics in the clinic that may be devoid of behavioral activity.

MicroRNA Targets for Asthma Therapy

Asthma is a chronic inflammatory obstructive lung disease that is stratified into endotypes. Th2 high asthma is due to an imbalance of Th1/Th2 signaling leading to abnormally high levels of Th2 cytokines, IL-4, IL-5, and IL-13 and in some cases a reduction in type I interferons. Some asthmatics express Th2 low, Th1/Th17 high phenotypes with or without eosinophilia. Most asthmatics with Th2 high phenotype respond to beta-adrenergic agonists, muscarinic antagonists, and inhaled corticosteroids. However, 5-10% of asthmatics are not well controlled by these therapies despite significant advances in lung immunology and the pathogenesis of severe asthma. This problem is being addressed by developing novel classes of anti-inflammatory agents. Numerous studies have established efficacy of targeting pro-inflammatory microRNAs in mouse models of mild/moderate and severe asthma. Current approaches employ microRNA mimics and antagonists designed for use in vivo. Chemically modified oligonucleotides have enhanced stability in blood, increased cell permeability, and optimized target specificity. Delivery to lung tissue limits clinical applications, but it is a tractable problem. Future studies need to define the most effective microRNA targets and effective delivery systems. Successful oligonucleotide drug candidates must have adequate lung cell uptake, high target specificity, and efficacy with tolerable off-target effects.

MicroRNA-98 reduces nerve growth factor expression in nicotine-induced airway remodeling

Evolving evidence suggests that nicotine may contribute to impaired asthma control by stimulating expression of nerve growth factor (NGF), a neurotrophin associated with airway remodeling and airway hyperresponsiveness. We explored the hypothesis that nicotine increases NGF by reducing lung fibroblast (LF) microRNA-98 (miR-98) and PPARγ levels, thus promoting airway remodeling. Levels of NGF, miR-98, PPARγ, fibronectin 1 (FN1), endothelin-1 (EDN1, herein referred to as ET-1), and collagen (COL1A1 and COL3A1) were measured in human LFs isolated from smoking donors, in mouse primary LFs exposed to nicotine (50 μg/ml), and in whole lung homogenates from mice chronically exposed to nicotine (100 μg/ml) in the drinking water. In selected studies, these pathways were manipulated in LFs with miR-98 inhibitor (anti-miR-98), miR-98 overexpression (miR-98 mimic), or the PPARγ agonist rosiglitazone. Compared with unexposed controls, nicotine increased NGF, FN1, ET-1, COL1A1, and COL3A1 expression in human and mouse LFs and mouse lung homogenates. In contrast, nicotine reduced miR-98 levels in LFs in vitro and in lung homogenates in vivo Treatment with anti-miR-98 alone was sufficient to recapitulate increases in NGF, FN1, and ET-1, whereas treatment with a miR-98 mimic significantly suppressed luciferase expression in cells transfected with a luciferase reporter linked to the putative seed sequence in the NGF 3'UTR and also abrogated nicotine-induced increases in NGF, FN1, and ET-1 in LFs. Similarly, rosiglitazone increased miR-98 and reversed nicotine-induced increases in NGF, FN1, and ET-1. Taken together, these findings demonstrate that nicotine-induced increases in NGF and other markers of airway remodeling are negatively regulated by miR-98.

Chronic Airway Allergy Induces Pro-Inflammatory Responses in the Brain of Wildtype Mice but Not 3xTgAD Mice

The effects of systemic inflammation on the pathogenesis of Alzheimer's disease (AD) are not clarified, both beneficial and deleterious effects being reported. Allergy is accompanied by a systemic inflammatory response and some epidemiological studies have reported a positive association between a history of allergy/asthma and dementia. To investigate whether chronic airway allergy influences the inflammatory status in the brain, AD-like pathology, and behaviour in relation to AD, we induced chronic airway allergy in triple transgenic AD (3xTgAD) and wildtype (WT) mice by repeated exposure to ovalbumin (OVA) as allergen. Behavioural tests relevant for hippocampus-dependent behaviour were performed. We found that allergy significantly increased the brain levels of immunoglobulin (Ig) G, IgE. In 3xTgAD mice, allergy increased the levels of decay accelerating factor and decreased the phosphorylation of p38. In contrast, allergy increased the levels of interleukin (IL)-1β and complement component 1q (C1q) in WT mice. Bronchoalveolar lavage fluid analysis confirmed eosinophilia in both genotypes, but the basal levels of eosinophils were lower in 3xTgAD mice. In summary, allergy induced predominantly anti-inflammatory effects in 3xTgAD mice, and pro-inflammatory effects in WT mice, thus being another potential factor to be considered when studying AD pathogenesis.

Functional characterization of 3D contractile smooth muscle tissues generated using a unique microfluidic 3D bioprinting technology

Conditions such as asthma and inflammatory bowel disease are characterized by aberrant smooth muscle contraction. It has proven difficult to develop human cell-based models that mimic acute muscle contraction in 2D in vitro cultures due to the nonphysiological chemical and mechanical properties of lab plastics that do not allow for muscle cell contraction. To enhance the relevance of in vitro models for human disease, we describe how functional 3D smooth muscle tissue that exhibits physiological and pharmacologically relevant acute contraction and relaxation responses can be reproducibly fabricated using a unique microfluidic 3D bioprinting technology. Primary human airway and intestinal smooth muscle cells were printed into rings of muscle tissue at high density and viability. Printed tissues contracted to physiological concentrations of histamine (0.01-100 μM) and relaxed to salbutamol, a pharmacological compound used to relieve asthmatic exacerbations. The addition of TGFβ to airway muscle rings induced an increase in unstimulated muscle shortening and a decreased response to salbutamol, a phenomenon which also occurs in chronic lung diseases. Results indicate that the 3D bioprinted smooth muscle is a physiologically relevant in vitro model that can be utilized to study disease pathways and the effects of novel therapeutics on acute contraction and chronic tissue stenosis.

p300 mediates the histone acetylation of ORMDL3 to affect airway inflammation and remodeling in asthma

BACKGROUND

Bronchial asthma is affected by both environmental and genetic factors. The orosomucoid 1-like protein 3 (ORMDL3) gene is related to childhood asthma and is involved in airway inflammation and airway remodeling. The ORMDL3 promoter contains binding sites for the histone acetylase p300. Gene expression can be affected by epigenetic modifications. This study aimed to investigate whether the p300-mediated histone acetylation (HAT) of ORMDL3 gene affects airway inflammation and remodeling in asthma.

METHODS

16HBE14o- cells were transfected with various concentrations of a wild-type p300 plasmid or p300HAT-deletion plasmids. A dual luciferase reporter assay was used to examine the effect of p300-mediated HAT on the ORMDL3 promoter. Thirty BALB/c mice were randomly divided into a control group, an ovalbumin (OVA)-induced asthma group and an asthma + C646 (a selective inhibitor of p300) group. Noninvasive lung function tests were conducted to examine airway hyperreactivity (AHR) in the different groups. HE and Masson's trichrome staining was performed to examine airway remodeling and inflammation. Immunohistochemistry, western blotting and real-time PCR were used to analyze ORMDL3 expression in lung tissues. ELISA and western blotting were used to evaluate the HAT status in lung tissue. The ChIP assay was used to determine the relationship of the ORMDL3 promoter to p300 or acetylated histone H3 (aceH3).

RESULTS

p300 activated transcription from the ORMDL3 promoter, resulting in an increase in endogenous ORMDL3 mRNA levels. ORMDL3 promoter activity was reduced when the HAT activity of p300 was lost. ORMDL3 expression was elevated, and HAT activity was high in the lung tissues of asthmatic mice. p300 and aceH3 bound to the promoter region of ORMDL3. In the asthma group, the amounts of p300 and aceH3 recruited to the ORMDL3 promoter were increased. C646 inhibited p300 expression and reduced HAT activity and aceH3 levels in asthmatic mice, thereby reducing ORMDL3 expression and relieving AHR and airway remodeling.

CONCLUSION

p300-mediated HAT modulates the expression of the asthma susceptibility gene ORMDL3, thereby improving the process of airway inflammation and remodeling in asthma.

Fibulin-1c regulates transforming growth factor-β activation in pulmonary tissue fibrosis

Tissue remodeling/fibrosis is a major feature of all fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). It is underpinned by accumulating extracellular matrix (ECM) proteins. Fibulin-1c (Fbln1c) is a matricellular ECM protein associated with lung fibrosis in both humans and mice, and stabilizes collagen formation. Here we discovered that Fbln1c was increased in the lung tissues of IPF patients and experimental bleomycin-induced pulmonary fibrosis. Fbln1c-deficient (-/-) mice had reduced pulmonary remodeling/fibrosis and improved lung function after bleomycin challenge. Fbln1c interacted with fibronectin, periostin and tenascin-c in collagen deposits following bleomycin challenge. In a novel mechanism of fibrosis Fbln1c bound to latent transforming growth factor (TGF)-β binding protein-1 (LTBP1) to induce TGF-β activation, and mediated downstream Smad3 phosphorylation/signaling. This process increased myofibroblast numbers and collagen deposition. Fbln1 and LTBP1 co-localized in lung tissues from IPF patients. Thus, Fbln1c may be a novel driver of TGF-β-induced fibrosis involving LTBP1 and may be an upstream therapeutic target.

shRNA-Induced Knockdown of a Bioinformatically Predicted Target IL10 Influences Functional Parameters in Spontaneously Hypertensive Rats with Asthma

One of the most common comorbid pathology is asthma and arterial hypertension. For experimental modeling of comorbidity we have used spontaneously hypertensive rats with ovalbumin (OVA)-induced asthma. Rats were randomly divided into three groups: control group, OVA-induced asthma group; OVA-induced asthma + IL10 shRNA interference group. Target gene (IL10) was predicted by ANDSystem. We have demonstrated that RNA-interference of IL10 affected cardiovascular (tested using Millar microcatheter system) as well as respiratory functions (tested using force-oscillation technique, Flexivent) in rats. We have shown that during RNA-interference of IL10 gene in vivo there were changes in both cardiac and lung function parameters. These changes in the cardiovascular parameters can be described as positive. But the more intensive heart workload can lead to exhaust and decompensation of the heart functions. Knockdown of IL10 gene in asthma modeling induces some positive changes in respiratory functions of asthmatic animals such as decreased elastance and increased compliance of the lungs, as well as less pronounced pathomorphological changes in the lung tissue. Thus, we provide the data about experimentally confirmed functionality changes of the target which was in silico predicted to be associated with both asthma and hypertension – in our new experimental model of comorbid pathology.

Changes in mucin 1 expression in a rat model of allergic airway inflammation

PURPOSE

To explore the distribution and expressional changes of mucin 1 (Muc1) in airway of rats with allergic airway inflammation.

MATERIALS AND METHODS

Ovalbumin (OVA) was used to induce acute allergic inflammation in male Wistar rats. The distributions and expressions of Muc1 in lungs of normal and model rats were assessed by immunohistochemical staining and western blotting, respectively.

RESULTS

Immunohistochemical staining showed that Muc1 distributed in airway epithelial cells with ciliates, but not those nonciliated cells. Mucin 1 protein expression in the lung was increased during the development of allergic airway inflammation when compared with the normal rats.

CONCLUSION

Mucin 1 distributes in the airway epithelial cells with ciliates and the expressional increase of Muc1 in lung may imply its functions on allergic inflammatory episodes.

Targeted HAS2 Expression Lessens Airway Responsiveness in Chronic Murine Allergic Airway Disease

Hyaluronan (HA), a major component of the extracellular matrix, is secreted by airway structural cells. Airway fibroblasts in allergic asthma secrete elevated levels of HA in association with increased HA synthase 2 (HAS2) expression. Thus, we hypothesized that HA accumulation in the airway wall may contribute to airway remodeling and hyperresponsiveness in allergic airways disease. To examine this hypothesis, transgenic mice in which the α-smooth muscle actin (α-SMA) promoter drives HAS2 expression were generated. Mixed male and female α-SMA-HAS2 mice (HAS2+ mice, n = 16; HAS2- mice, n = 13) were sensitized via intraperitoneal injection and then chronically challenged with aerosolized ovalbumin (OVA) for 6 weeks. To test airway responsiveness, increasing doses of methacholine were delivered intravenously and airway resistance was measured using the forced oscillation technique. HA, cytokines, and cell types were analyzed in bronchoalveolar lavage fluid, serum, and whole lung homogenates. Lung sections were stained using antibodies specific for HA-binding protein (HABP) and α-SMA, as well as Masson's trichrome stain. Staining of lung tissue demonstrated significantly increased peribronchial HA, α-SMA, and collagen deposition in OVA-challenged α-SMA-HAS2+ mice compared with α-SMA-HAS2- mice. Unexpectedly, OVA-challenged α-SMA-HAS2+ mice displayed significantly reduced airway responsiveness to methacholine compared with similarly treated α-SMA-HAS2- mice. The total numbers of inflammatory cell types in the bronchoalveolar lavage fluid did not differ significantly between OVA-challenged α-SMA-HAS2+ mice and α-SMA-HAS2- mice. We conclude that allergen-challenged mice that overexpress HAS2 in myofibroblasts and smooth muscle cells develop increased airway fibrosis, which lessens airway hyperresponsiveness to bronchoconstrictors.

ORMDL3 may participate in the pathogenesis of bronchial epithelial‑mesenchymal transition in asthmatic mice with airway remodeling

Asthma is a common chronic respiratory disease in children that is caused by a complex interaction between genetic and environmental factors. Orosomucoid‑like 3 (ORMDL3) is a candidate gene that has been strongly associated with asthma; however, the underlying mechanisms are unknown. ORMDL3 regulates the expression of metalloproteinases and transforming growth factor‑β, and ORMDL3 transgenic mice exhibit increased airway remodeling. Therefore, ORMDL3 may be associated with airway remodeling. The present study attempted to examine the associations between ORMDL3 and the severity of airway remodeling in asthmatic mice, and also to determine whether ORMDL3 induces epithelial‑mesenchymal transition (EMT) in the bronchial epithelium. For this purpose, BALB/c mice were randomly assigned to control and asthma groups. Lung tissues were collected on days 3, 7 and 14 of the ovalbumin (OVA) challenge. Airway remodeling in asthmatic mice was then observed by hematoxylin and eosin, and Masson staining. Morphological changes in the bronchial epithelium were assessed by transmission electron microscopy. The EMT‑associated indicators E‑cadherin (E‑cad), fibroblast‑specific protein 1 (FSP1) and Vimentin (VIM) were assessed by western blotting and reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) at different time points of airway remodeling in asthmatic mice to detect the trend in EMT. Then, the localization of ORMDL3 was observed by immunohistochemistry, and its protein and mRNA expression was examined by western blotting and RT‑qPCR, respectively. Furthermore, the bronchial epithelial cell line 16HBE14o‑was transfected with an ORMDL3‑expressing plasmid, and the differences in E‑cad, FSP‑1 and VIM expression were detected by immunofluorescence, western blotting and RT‑qPCR; the cell invasive ability was assessed by microscopy. The results revealed that ORMDL3 expression in the bronchial epithelium was associated with airway remodeling and EMT progression in vivo. Transfection of ORMDL3 into 16HBE 14o‑cells in vitro induced EMT. Taken together, these findings suggest that ORMDL3 may regulate EMT in the bronchial epithelium, thereby affecting airway remodeling in asthma.

Effects of Aspergillus fumigatus on glucocorticoid receptor and β2-adrenergic receptor expression in a rat model of asthma

PURPOSE

Conventional inhaled corticosteroids or β2-adrenergic receptor agonists do not work well in some asthmatic populations while empirical antifungal therapy has obvious impact on those patients. The study was designed to investigate whether short-term exposure to Aspergillus fumigatus (A. fumigatus) could decrease glucocorticoid receptor (GCR) and β2-adrenergic receptor (ADRB2) expression in lung tissue of asthmatic rats.

MATERIALS AND METHODS

A rat model of chronic asthma was first established by ovalbumin sensitization and challenge. Rats with chronic asthma were then exposed to short-term application of A. fumigatus spores. Airway hyper-responsiveness, eosinophil ratio in bronchoalveolar lavage (BAL) fluid and total IgE in serum were counted in these experimental animals. GCR and ADRB2 expression in the lung were detected and analyzed. Furthermore, the levels of toll-like receptors (TLRs) 2, 3 and 4 in lung tissue were measured.

RESULTS

Short-term exposure to A. fumigatus could down-regulate the expression of GCR, aggravate airway hyper-responsiveness and increase the level of TLR2 in rats with asthma. There were no obvious changes in the levels of ADRB2 expression, recruited eosinophils, total IgE, TLR3 and TLR4 after application of A. fumigatus in asthmatic rats.

CONCLUSIONS

These findings indicate that A. fumigatus exposure may be involved in glucocorticoids unresponsiveness by down-regulating the expression of GCR in asthmatics. The possibility of A. fumigatus colonization or infection should not be ignored in patients of steroid-resistant asthma.

Bacillus Calmette-Guerin alleviates airway inflammation and remodeling by preventing TGF-β1 induced epithelial-mesenchymal transition

Bacillus Calmette-Guerin (BCG) is a potent agent for the prevention of tuberculosis. Current studies have regarded BCG as an immunomodulator. However, there is little information on whether it can be used to inhibit airway inflammation and airway remodeling caused by asthma. Therefore, in this study, we investigate the role of epithelial-mesenchymal transition (EMT) in airway inflammation and airway remodeling as well as the possible therapeutic mechanism of BCG for the treatment of asthma. Wistar rats were sensitized and challenged by ovalbumin for 2 weeks or 8 weeks. BCG was subcutaneously administered daily before every ovalbumin challenge to determine its therapeutic effects. The 2 weeks model group showed extensive eosinophilia, chronic inflammatory responses, bronchial wall thickening, airway epithelium damage, increased levels of transforming growth factor β 1 (TGF-β₁) in both bronchoalveolar lavage fluid and sera, decreased expression of epithelial marker E-cadherin, and increased expressions of mesenchymal markers α-smooth muscle actin (α-SMA) and Fibronectin (Fn). Except for inflammatory responses, all responses were more significant in the 8 weeks model group which displayed characteristics of airway remodeling including subepithelial fibrosis, smooth muscle hypertrophy, and goblet cell hyperplasia. When compared with the model groups, BCG administration inhibited airway inflammation and airway remodeling, decreased TGF-β₁ levels, upregulated expression of E-cadherin, and downregulated expression of α-SMA and Fn. The present study suggests for the first time that increased secretion of TGF- β₁ induced by asthmatic chronic inflammation may result in EMT, which is one of the most important mechanisms of airway inflammation and airway remodeling seen with asthma. BCG alleviates airway inflammation and airway remodeling by preventing TGF-β₁ induced EMT, therefore BCG may be a new therapy for treating asthma.

Effects of an early intervention using human amniotic epithelial cells in a COPD rat model

The study aimed to investigate the effect of an early intervention using human amniotic epithelial cell (hAEC) in a rat model of chronic obstructive pulmonary disease (COPD). Twenty-four specific pathogen-free Wistar rats were randomized to the control, COPD, and COPD+hAEC groups. COPD was established by intratracheal LPS injection combined with smoke fumigation over 30days. On the first day of model establishment rats in the AEC group also received intratracheal instillation of 500,000 hAECs isolated from the placenta of healthy donors. The mean linear intercept (MLI) and mean alveolar number (MAN) were used to assess the degree of lung emphysema. IL-8 was measured using a radioimmunoassay, surfactant protein D (SP-D) was measured by ELISA, and matrix metalloproteinase (MMP)2 and MMP8 expression was assessed by PCR. Smoke fumigation combined to LPS injection successfully established a COPD rat model with significant emphysema and airway inflammation, elevated MLI and MAN, elevated systemic and lung tissue levels of IL-8 and SP-D (P<0.05), and high expression of MMP2 and MMP8. Rats in the COPD+hAEC group exhibited alleviated lung damage, MLI and MAN (P<0.05), reduced systemic and lung tissue levels of IL-8 and SP-D (P<0.05) and MMP2 and MMP8 expression (P<0.05). Early intervention using hAECs could delay disease progression in rats with COPD.

Activation of angiotensin-converting enzyme 2 (ACE2) attenuates allergic airway inflammation in rat asthma model

Angiotensin-I converting enzyme (ACE) is positively correlated to asthma, chronic obstructive pulmonary disease (COPD), acute respiratory distress syndrome (ARDS) and is highly expressed in lungs. ACE2, the counteracting enzyme of ACE, was proven to be protective in pulmonary, cardiovascular diseases. In the present study we checked the effect of ACE2 activation in animal model of asthma. Asthma was induced in male wistar rats by sensitization and challenge with ovalbumin and then treated with ACE2 activator, diminazene aceturate (DIZE) for 2weeks. 48h after last allergen challenge, animals were anesthetized, blood, BALF, femoral bone marrow lavage were collected for leucocyte count; trachea for measuring airway responsiveness to carbachol; lungs and heart were isolated for histological studies and western blotting. In our animal model, the characteristic features of asthma such as altered airway responsiveness to carbachol, eosinophilia and neutrophilia were observed. Western blotting revealed the increased pulmonary expression of ACE1, IL-1β, IL-4, NF-κB, BCL2, p-AKT, p-p38 and decreased expression of ACE2 and IκB. DIZE treatment prevented these alterations. Intraalveolar interstitial thickening, inflammatory cell infiltration, interstitial fibrosis, oxidative stress and right ventricular hypertrophy in asthma control animals were also reversed by DIZE treatment. Activation of ACE2 by DIZE conferred protection against asthma as evident from biochemical, functional, histological and molecular parameters. To the best of our knowledge, we report for the first time that activation of ACE2 by DIZE prevents asthma progression by altering AKT, p38, NF-κB and other inflammatory markers.

Fibulin-1 regulates the pathogenesis of tissue remodeling in respiratory diseases

Airway and/or lung remodeling, involving exaggerated extracellular matrix (ECM) protein deposition, is a critical feature common to pulmonary diseases including chronic obstructive pulmonary disease (COPD), asthma, and idiopathic pulmonary fibrosis (IPF). Fibulin-1 (Fbln1), an important ECM protein involved in matrix organization, may be involved in the pathogenesis of these diseases. We found that Fbln1 was increased in COPD patients and in cigarette smoke-induced (CS-induced) experimental COPD in mice. Genetic or therapeutic inhibition of Fbln1c protected against CS-induced airway fibrosis and emphysema-like alveolar enlargement. In experimental COPD, this occurred through disrupted collagen organization and interactions with fibronectin, periostin, and tenascin-c. Genetic inhibition of Fbln1c also reduced levels of pulmonary inflammatory cells and proinflammatory cytokines/chemokines (TNF-α, IL-33, and CXCL1) in experimental COPD. Fbln1c^-/- mice also had reduced airway remodeling in experimental chronic asthma and pulmonary fibrosis. Our data show that Fbln1c may be a therapeutic target in chronic respiratory diseases.

Genetic Deletion of β-Arrestin-2 and the Mitigation of Established Airway Hyperresponsiveness in a Murine Asthma Model

β-Arrestin-2 (βarr2) is a ubiquitously expressed cytosolic protein that terminates G protein-coupled receptor signaling and transduces G protein-independent signaling. We previously showed that mice lacking βarr2 do not develop an asthma phenotype when sensitized to, and challenged with, allergens. The current study evaluates if an established asthma phenotype can be mitigated by deletion of βarr2 using an inducible Cre recombinase. We sensitized and challenged mice to ovalbumin (OVA) and demonstrated that on Day (d) 24 the allergic asthma phenotype was apparent in uninduced βarr2 and wild-type (WT) mice. In a second group of OVA-treated mice, tamoxifen was injected on d24 to d28 to activate Cre recombinase, and OVA aerosol challenge was continued through d44. The asthma phenotype was assessed using lung mechanics measurements, bronchoalveolar lavage cell analysis, and histological assessment of mucin and airway inflammation. Compared with their respective saline-treated controls, OVA-treated WT mice and mice expressing the inducible Cre recombinase displayed a significant asthma phenotype at d45. Whereas tamoxifen treatment had no significant effect on the asthma phenotype in WT mice, it inhibited βarr2 expression and caused a significant reduction in airway hyper-responsiveness (AHR) in Cre-inducible mice. These findings suggest that βarr2 is actively required for perpetuation of the AHR component of the allergic asthma phenotype. Our finding that βarr2 participates in the perpetuation of AHR in an asthma model means that targeting βarr2 may provide immediate and potentially long-term relief from daily asthma symptoms due to AHR irrespective of inflammation.

Inflammation and infections in asthma

INTRODUCTION

Asthma is driven by an inflammatory response against normally harmless environmental inorganic and organic compounds in the respiratory tract. Immune responses to airborne pathogens such as viruses and bacteria may reduce the allergic responses but are also known to trigger asthma attacks and eventually lead to severe disease condition.

OBJECTIVE

To investigate the role of respiratory pathogens concerning the induction or protection against acute or chronic asthma manifestations.

METHODS

We included 131 articles for the final review according to their relevance with the subject.

RESULTS

There is apparently contradictory interaction of respiratory germs in the airways of asthmatics which may be protective on one angle but deleterious on the other.

CONCLUSION

The relationship between inflammation and remodeling and the pathogenic role of viral and bacterial infection in the airways of asthmatic patients is still highly debatable and incompletely understood.

Roxithromycin suppresses airway remodeling and modulates the expression of caveolin-1 and phospho-p42/p44MAPK in asthmatic rats

Roxithromycin (RXM) expresses anti-asthmatic effects that are separate from its antibiotic activity, but its effects on airway remodeling are still unknown. Here, we evaluated the effects of RXM on airway remodeling and the expression of caveolin-1 and phospho-p42/p44mitogen-activated protein kinase (phospho-p42/p44MAPK) in chronic asthmatic rats. The chronic asthma was induced by ovalbumin/Al(OH)3 sensitization and ovalbumin challenge, RXM (30mg/kg) or dexamethasone (0.5mg/kg) was given before airway challenge initiation. We measured the thickness of bronchial wall and bronchial smooth muscle cell layer to indicate airway remodeling, and caveolin-1 and phospho-p42/p44MAPK expression in lung tissue and airway smooth muscle were detected by immunohistochemistry and western blot analysis, respectively. The results demonstrated that RXM treatment decreased the thickness of bronchial wall and bronchial smooth muscle cell layer, and also downregulated the phospho-p42/p44MAPK expression and upregulated the caveolin-1 expression. The above effects of RXM were similar to dexamethasone. Our results suggested that pretreatment with RXM could suppress airway remodeling and regulate the expression of caveolin-1 and phospho-p42/p44MAPK in chronic asthmatic rats.

Airway wall remodeling in young and adult rats with experimentally provoked bronchial asthma

BACKGROUND

Airway wall remodeling is a typical finding in patients suffering from bronchial asthma. While morphological changes have been thoroughly described in adults, less is known about such changes in children because of the limited accessibility of relevant material. To overcome this constraint, animal asthma models may be used instead of human specimens. This study examined rats with artificially stimulated chronic asthma-like symptoms.

METHODS

Brown Norway rats of two age categories (young and adult) were sensitized by ovalbumin (OA), and their intrapulmonary airways (IA) were studied using morphometric and histochemical methods.

RESULTS

OA administration induced a significant increase in lung resistance in young animals but not in adults. The total IA wall area was significantly increased in both young and adult OA rats. In young animals, thickening of the adventitia played a more crucial role in this increase than it did in adults, in which the mucosa and the submucosa participated to a higher degree. The IA walls of young OA rats had significantly higher levels of infiltrating eosinophils than those of adult OA animals. The multiplication of goblet cells was more pronounced in adult rats, which was associated with a tendency to produce a higher proportion of acidic glycoconjugates.

CONCLUSIONS

OA stimulation affected the IA of young rats differently than those of adult animals. Changes in the outer IA layer of young rats can be triggered by activated eosinophils; however, stimulated airway epithelium can be a source of factors that influence the inner IA layers in adult rats.

AVE 0991, a non-peptide mimic of angiotensin-(1-7) effects, attenuates pulmonary remodelling in a model of chronic asthma

BACKGROUND AND PURPOSE

AVE 0991 (AVE) is a non-peptide compound, mimic of the angiotensin (Ang)-(1-7) actions in many tissues and pathophysiological states. Here, we have investigated the effect of AVE on pulmonary remodelling in a murine model of ovalbumin (OVA)-induced chronic allergic lung inflammation.

EXPERIMENTAL APPROACH

We used BALB/c mice (6-8 weeks old) and induced chronic allergic lung inflammation by OVA sensitization (20 μg·mouse(-1) , i.p., four times, 14 days apart) and OVA challenge (1%, nebulised during 30 min, three times per·week, for 4 weeks). Control and AVE groups were given saline i.p and challenged with saline. AVE treatment (1 mg·kg(-1) ·per day, s.c.) or saline (100 μL·kg(-1) ·per day, s.c.) was given during the challenge period. Mice were anaesthetized 72 h after the last challenge and blood and lungs collected. In some animals, primary bronchi were isolated to test contractile responses. Cytokines were evaluated in bronchoalveolar lavage (BAL) and lung homogenates.

KEY RESULTS

Treatment with AVE of OVA sensitised and challenged mice attenuated the altered contractile response to carbachol in bronchial rings and reversed the increased airway wall and pulmonary vasculature thickness and right ventricular hypertrophy. Furthermore, AVE reduced IL-5 and increased IL-10 levels in the BAL, accompanied by decreased Ang II levels in lungs.

CONCLUSIONS AND IMPLICATIONS

AVE treatment prevented pulmonary remodelling, inflammation and right ventricular hypertrophy in OVA mice, suggesting that Ang-(1-7) receptor agonists are a new possibility for the treatment of pulmonary remodelling induced by chronic asthma.

Time- and concentration-dependent genomic responses of the rat airway to inhaled nickel subsulfide

OBJECTIVE

To provide insights into the mode of action for Ni3S2 lung carcinogenicity by examining gene expression changes in target cells after inhalation exposure.

METHODS

Gene expression changes were determined in micro-dissected lung broncho-alveolar cells from Fischer 344 rats following inhalation of Ni3S2 at 0.0, 0.04, 0.08, 0.15, and 0.60 mg/m(3) (0.03, 0.06, 0.11, and 0.44 mgNi/m(3)) for one and four weeks (6h/day, 5 days/week).

RESULTS

Broncho-alveolar lavage fluid evaluation and lung histopathology provided evidence of inflammation only at the two highest concentrations, which were similar to those tested in the 2-year bioassay. The number of statistically significant up- and down-regulated genes decreased markedly from one to four weeks of exposure, suggesting adaptation. Cell signal pathway enrichment at both time-points primarily reflected responses to toxicity, including inflammatory and proliferative signaling. While proliferative signaling was up-regulated at both time points, some inflammatory signaling reversed from down-regulation at 1 week to up-regulation at 4 weeks.

CONCLUSIONS

These results support a mode of action for Ni3S2 carcinogenicity driven by chronic toxicity, inflammation and proliferation, leading to mis-replication, rather than by direct genotoxicity. Benchmark dose (BMD) analysis identified the lowest pathway transcriptional BMD exposure concentration as 0.026 mgNi/m(3), for apoptosis/survival signaling. When conducted on the basis of lung Ni concentration the lowest pathway BMD was 0.64 μgNi/g lung, for immune/inflammatory signaling.

IMPLICATIONS

These highly conservative BMDs could be used to derive a point of departure in a nonlinear risk assessment for Ni3S2 toxicity and carcinogenicity.

Effects of chronic exposure to Aspergillus fumigatus on epidermal growth factor receptor expression in the airway epithelial cells of asthmatic rats

Epidemiologic studies suggest that increased concentrations of airborne spores of Aspergillus fumigatus closely relate to asthma aggravation. Chronic exposure to A. fumigatus aggravates airway inflammation, remodeling, and airway hyperresponsiveness in asthmatic rats. The effects of chronic exposure to A. fumigatus on epidermal growth factor receptor (EGFR) expression in the airway epithelial cells of asthmatic rats remain unclear. This study aimed to investigate the effects of chronic exposure to A. fumigatus on injury and shedding of airway epithelium, goblet cell metaplasia, and EGFR expression in the airway epithelial cells of asthmatic rats. A rat model of chronic asthma was established using ovalbumin (OVA) sensitization and challenge. Rats with chronic asthma were then exposed to long-term inhalation of spores of A. fumigatus, and the dynamic changes in injury and shedding of airway epithelium, goblet cell metaplasia, and EGFR expression were observed and analyzed. Chronic exposure to A. fumigatus could aggravate airway epithelial cell damage, upregulate the expression of EGFR and its ligands EGF and TGF-α, promote goblet cell metaplasia, and increase airway responsiveness in rats with asthma. Chronic exposure to A. fumigatus upregulates the expression of EGFR and its ligands in asthmatic rats. The EGFR pathway may play a role in asthma aggravation induced by exposure to A. fumigatus.

The effects of Valeriana officinalis L. hydro-alcoholic extract on depression like behavior in ovalbumin sensitized rats

Background:

Neuroimmune factors have been considered as contributors to the pathogenesis of depression. Beside other therapeutic effects, Valeriana officinalis L., have been suggested to have anti-inflammatory effects. In the present study, the effects of V. officinalis L. hydro alcoholic extract was investigated on depression like behavior in ovalbumin sensitized rats.

Materials and Methods:

A total of 50 Wistar rats were divided into five groups: Group 1 (control group) received saline instead of Valeriana officinalis L. extract. The animals in group 2 (sensitized) were treated by saline instead of the extract and were sensitized using the ovalbumin. Groups 3-5 (Sent - Ext 50), (Sent - Ext 100) and (Sent - Ext 200) were treated by 50, 100 and 200 mg/kg of V. officinalis L. hydro-alcoholic extract respectively, during the sensitization protocol. Forced swimming test was performed for all groups and immobility time was recorded. Finally, the animals were placed in the open-field apparatus and the crossing number on peripheral and central areas was observed.

Results:

The immobility time in the sensitized group was higher than that in the control group (P < 0.01). The animals in Sent-Ext 100 and Sent-Ext 200 groups had lower immobility times in comparison with sensitized group (P < 0.05 and P < 0.01). In the open field test, the crossed number in peripheral by the sensitized group was higher than that of the control one (P < 0.01) while, the animals of Sent-Ext 50, Sent-Ext 100 and Sent-Ext 200 groups had lower crossing number in peripheral compared with the sensitized group (P < 0.05 and P < 0.01 respectively). Furthermore, in the sensitized group, the central crossing number was lower than that of the control group (P < 0.001). In the animals treated by 200 mg/kg of the extract, the central crossing number was higher than that of the sensitized group (P < 0. 05).

Conclusions:

The results of the present study showed that the hydro-alcoholic extract of V. officinalis prevents depression like behavior in ovalbumin sensitized rats. These results support the traditional belief on the about beneficial effects of V. officinalis in the nervous system. Moreover, further investigations are required in order to better understand this protective effect.

Differential effects of allergen challenge on large and small airway reactivity in mice

The relative contributions of large and small airways to hyperresponsiveness in asthma have yet to be fully assessed. This study used a mouse model of chronic allergic airways disease to induce inflammation and remodelling and determine whether in vivo hyperresponsiveness to methacholine is consistent with in vitro reactivity of trachea and small airways. Balb/C mice were sensitised (days 0, 14) and challenged (3 times/week, 6 weeks) with ovalbumin. Airway reactivity was compared with saline-challenged controls in vivo assessing whole lung resistance, and in vitro measuring the force of tracheal contraction and the magnitude/rate of small airway narrowing within lung slices. Increased airway inflammation, epithelial remodelling and fibrosis were evident following allergen challenge. In vivo hyperresponsiveness to methacholine was maintained in isolated trachea. In contrast, methacholine induced slower narrowing, with reduced potency in small airways compared to controls. In vitro incubation with IL-1/TNFα did not alter reactivity. The hyporesponsiveness to methacholine in small airways within lung slices following chronic ovalbumin challenge was unexpected, given hyperresponsiveness to the same agonist both in vivo and in vitro in tracheal preparations. This finding may reflect the altered interactions of small airways with surrounding parenchymal tissue after allergen challenge to oppose airway narrowing and closure.

Role of CXCL13 in cigarette smoke-induced lymphoid follicle formation and chronic obstructive pulmonary disease

RATIONALE

The B cell-attracting chemokine CXCL13 is an important mediator in the formation of tertiary lymphoid organs (TLOs). Increased numbers of ectopic lymphoid follicles have been observed in lungs of patients with severe chronic obstructive pulmonary disease (COPD). However, the role of these TLOs in the pathogenesis of COPD remains unknown.

OBJECTIVES

By neutralizing CXCL13 in a mouse model of chronic cigarette smoke (CS) exposure, we aimed at interrogating the link between lymphoid follicles and development of pulmonary inflammation, emphysema, and airway wall remodeling.

METHODS

We first quantified and localized CXCL13 in lungs of air- or CS-exposed mice and in lungs of never smokers, smokers without airflow obstruction, and patients with COPD by reverse transcriptase-polymerase chain reaction, ELISA, and immunohistochemistry. Next, CXCL13 signaling was blocked by prophylactic or therapeutic administration of anti-CXCL13 antibodies in mice exposed to air or CS for 24 weeks, and several hallmarks of COPD were evaluated.

MEASUREMENTS AND MAIN RESULTS

Both mRNA and protein levels of CXCL13 were increased in lungs of CS-exposed mice and patients with COPD. Importantly, expression of CXCL13 was observed within B-cell areas of lymphoid follicles. Prophylactic and therapeutic administration of anti-CXCL13 antibodies completely prevented the CS-induced formation of pulmonary lymphoid follicles in mice. Interestingly, absence of TLOs attenuated destruction of alveolar walls and inflammation in bronchoalveolar lavage but did not affect airway wall remodeling.

CONCLUSIONS

CXCL13 is produced within lymphoid follicles of patients with COPD and is crucial for the formation of TLOs. Neutralization of CXCL13 partially protects mice against CS-induced inflammation in bronchoalveolar lavage and alveolar wall destruction.

A time course study on the development of allergen-induced nasal airway remodeling in a rat model

BACKGROUND

Only a few studies have investigated the airway remodeling process in allergic rhinitis (AR), and the results reported are conflicting. We established an allergen-induced nasal remodeling model for AR using brown Norway rats and investigated time-dependent histological changes and the reversibility of the epithelial and subepithelial changes.

METHODS

Ovalbumin (OVA)-sensitized rats were exposed to OVA daily and then assigned to one of five groups depending on the duration of the challenge. Groups I, II, III, and IV rats were exposed for 1, 4, 8, and 12 weeks, respectively. Group V rats were exposed for 12 weeks and then protected from challenge for 4 weeks. Matched control rats were exposed to saline. Histological parameters of the nasal mucosa such as epithelial and subepithelial thickness, goblet cell hyperplasia, eosinophil infiltration, submucosal gland hypertrophy, and expression of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were compared between groups.

RESULTS

Repeated challenges for 12 weeks resulted in the characteristic features of nasal airway remodeling. All parameters except epithelial thickness increased markedly. Goblet cell hyperplasia and eosinophil infiltration decreased to control group levels after cessation of challenge for 4 weeks. Subepithelial changes such as subepithelial thickening, submucosal gland hypertrophy, and increased expression of MMP-9 and TIMP-1 were still observed after 4 weeks without challenge.

CONCLUSION

Our results indicate that prolonged OVA challenge can induce nasal remodeling. Epithelial changes were minimal or absent after cessation of the challenge, but subepithelial changes were resistant to reversal.

Fractionated irradiations lead to chronic allergic airway inflammation through increasing the influx of macrophages

OBJECTIVE

In our previous study, repeated irradiations showed persistent depression of immune response, especially Th1-related immune response. Here, we hypothesized and determined that irradiation may exacerbate development of allergic airway inflammation.

METHODS

C57BL/6 mice were irradiated repeatedly at 1 Gy or 0.5 Gy. At 6 months after irradiation, mice were sensitized and challenged short-term with OVA. Antigen-specific immunoglobulins, the percentages of inflammatory cells, chemokine expression, cytokine levels, and collagen deposition were tested.

RESULTS

In irradiated mice, IgG2a in serum was lower when compared with that of control mice, while IgG1 was significantly higher. Interestingly, the percentages of macrophages in bronchoalveolar lavage fluid (BALF) and the lung of irradiated mice were significantly higher. Conversely, the percentages of neutrophil were significantly lower in BALF of irradiated mice. In the lung of irradiated mice, MCP-1 and IP-10 for attraction of macrophages showed the higher expression level, but KC expression for neutrophils showed no difference. Next, TGF-β1 and IL-17A in BALF were higher in irradiated mice. In addition, phosphorylated-Smad2/3 was increased in irradiated mice. Finally, the deposition of collagen was increased in irradiated mice.

CONCLUSION

Our study showed that fractionated irradiation lead to the chronic allergic airway inflammation through increasing the influx of macrophages and active TGF-β levels.

Increased mast cell density and airway responses to allergic and non-allergic stimuli in a sheep model of chronic asthma

Background

Increased mast cell (MC) density and changes in their distribution in airway tissues is thought to contribute significantly to the pathophysiology of asthma. However, the time sequence for these changes and how they impact small airway function in asthma is not fully understood. The aim of the current study was to characterise temporal changes in airway MC density and correlate these changes with functional airway responses in sheep chronically challenged with house dust mite (HDM) allergen.

Methodology/Principal Findings

MC density was examined on lung tissue from four spatially separate lung segments of allergic sheep which received weekly challenges with HDM allergen for 0, 8, 16 or 24 weeks. Lung tissue was collected from each segment 7 days following the final challenge. The density of tryptase-positive and chymase-positive MCs (MC_T and MC_TC respectively) was assessed by morphometric analysis of airway sections immunohistochemically stained with antibodies against MC tryptase and chymase.

MC_T and MC_TC density was increased in small bronchi following 24 weeks of HDM challenges compared with controls (P<0.05). The MC_TC/MC_T ratio was significantly increased in HDM challenged sheep compared to controls (P<0.05). MC_T and MC_TC density was inversely correlated with allergen-induced increases in peripheral airway resistance after 24 weeks of allergen exposure (P<0.05). MC_T density was also negatively correlated with airway responsiveness after 24 challenges (P<0.01).

Conclusions

MC_T and MC_TC density in the small airways correlates with better lung function in this sheep model of chronic asthma. Whether this finding indicates that under some conditions mast cells have protective activities in asthma, or that other explanations are to be considered requires further investigation.

Cigarette smoke dissociates inflammation and lung remodeling in OVA-sensitized and challenged mice

We evaluated the effects of cigarette smoke (CS) on lung inflammation and remodeling in a model of ovalbumin (OVA)-sensitized and OVA-challenged mice. Male BALB/c mice were divided into 4 groups: non-sensitized and air-exposed (control); non-sensitized and exposed to cigarette smoke (CS), sensitized and air-exposed (OVA) (50 μg+OVA 1% 3 times/week for 3 weeks) and sensitized and cigarette smoke exposed mice (OVA+CS). IgE levels were not affected by CS exposure. The increases in total bronchoalveolar fluid cells in the OVA group were attenuated by co-exposure to CS, as were the changes in IL-4, IL-5, and eotaxin levels as well as tissue elastance (p<0.05). In contrast, only the OVA+CS group showed a significant increase in the protein expression of IFN-γ, VEGF, GM-CSF and collagen fiber content (p<0.05). In our study, exposure to cigarette smoke in OVA-challenged mice resulted in an attenuation of pulmonary inflammation but led to an increase in pulmonary remodeling and resulted in the dissociation of airway inflammation from lung remodeling.

Chronic Aspergillus fumigatus exposure upregulates the expression of mucin 5AC in the airways of asthmatic rats

BACKGROUND

Airway mucus hypersecretion is associated with increased morbidity and mortality in patients with asthma. Chronic Aspergillus fumigatus (A. fumigatus) exposure leads to aggravation of airway inflammation and remodeling, including goblet cell hyperplasia (GCH) and mucus hypersecretion in a rat model of asthma. The effects of chronic A. fumigatus exposure on the expression of airway mucin 5AC (MUC5AC) are unknown.

METHODS

The rat model of chronic asthma was set up by systemic sensitization and repeated challenge to ovalbumin (OVA). The asthmatic rats were exposed to chronic intranasal inhalation of A. fumigatus spores. The changes of MUC5AC expression, the extent of GCH, and airway hyperreactivity (AHR) were measured after exposure to the fungus.

RESULTS AND CONCLUSIONS

Chronic exposure to A. fumigatus upregulates the expression of MUC5AC, and induces GCH in the airways of asthma rats, and the remodeling changes of the airway epithelium was positively correlated with AHR. Upregulation of MUC5AC and induction of GCH may be mechanisms by which chronic A. fumigatus exposure promotes the progression of asthma.

[Morphological changes following airway remodeling in asthmatic rats]

OBJECTIVE

To explore the establishment of an asthmatic model with airway remodeling in rats by observing the morphological changes of the airway in different stages.

METHODS

Animals were divided into two groups: asthmatic group and control group. The subjects were observed at 5 phases: before activation and 2, 4, 6, 8 weeks after activation. General histological changes were observed using hematoxylin and eosin stained sections. Being standardized by internal perimeter (Pi), the wall thickness (d), internal area (Ai), outer area (Ao) and wall area (WA) of the airway were quantified by computer-assisted image analysis system. And the membrane airways were divided into 3 grades (large, media and small airways) to be analyzed.

RESULTS

The changes of small airway appeared earlier and greater than the others. The changes of media airway appeared later than the small one. The changes of large airway appeared as later as the 4th week after activation. There were no differences before and after activation in control group (P>0.05).

CONCLUSION

(1) Prolonged, repeated and low density Ag activation could establish asthmatic model with airway remodeling. (2) The morphological changes of the airways increased following airway remodeling, and the greatest increase occurred at small airway. (3)The morphological changes in the model rats were similar to that in human beings.

Urotensin upregulates transforming growth factor-β1 expression of asthma airway through ERK-dependent pathway

Airway smooth muscle cells (ASMCs) play a key role in the process of asthma airway remodeling. Urotensin II (UII) and transforming growth factor (TGF)-β are potent mitogens for ASMCs proliferation. The study was aimed to determine whether UII-upregulated TGF-β-mediated ASMCs proliferation and extracellular signal-regulated kinase (ERK) was required for such an effect. OVA-sensitized rats were challenged to induce asthma. Lung morphology and airway dynamic parameters were monitored. ASMCs from control and asthma rats were purified for the measurement of UII and TGF-β1 expression. In vitro experiments were conducted to determine the direct effect of UII on TGF-β1 expression by ASMCs. Finally, U0126, an ERK inhibitor was used to examine the role of ERK pathway in UII mediated TGF-β1 upregulation. We found that both UII and TGF-β1 were upregulated in asthma lung tissues. In vitro study on ASMCs further revealed that UII may render its effect on ASMCs cells through the upregulation of TGF-β1. Data also supported the conclusion that ERK pathway was required, but not sufficient in UII-induced TGF-β1 upregulation. The current study provides new evidence that UII is involved in the TGF-β mediated mitogenic effect on ASMCs. UII, at least partially, uses ERK pathway to render such effect.

Assessment of peripheral airway function following chronic allergen challenge in a sheep model of asthma

Background

There is increasing evidence that the small airways contribute significantly to the pathophysiology of asthma. However, due to the difficulty in accessing distal lung regions in clinical settings, functional changes in the peripheral airways are often overlooked in studies of asthmatic patients. The aim of the current study was to characterize progressive changes in small airway function in sheep repeatedly challenged with house dust mite (HDM) allergen.

Methodology/Principal Findings

Four spatially separate lung segments were utilized for HDM challenges. The right apical, right medial, right caudal and left caudal lung segments received 0, 8, 16 and 24 weekly challenges with HDM respectively. A wedged-bronchoscope technique was used to assess changes in peripheral resistance (R_p) at rest, and in response to specific and non-specific stimuli throughout the trial. Allergen induced inflammatory cell infiltration into bronchoalveolar lavage and increases in R_p in response to HDM and methacholine were localized to treated lung segments, with no changes observed in adjacent lung segments. The acute response to HDM was variable between sheep, and was significantly correlated to airway responsiveness to methacholine (r_s = 0.095, P<0.01). There was no correlation between resting R_p and the number of weeks of HDM exposure. Nor was there a correlation between the magnitude of early-phase airway response and the number of HDM-challenges.

Conclusions

Our findings indicate that airway responses to allergic and non-allergic stimuli are localized to specific treated areas of the lung. Furthermore, while there was a decline in peripheral airway function with HDM exposure, this decrease was not correlated with the length of allergen challenge.

Small animals models for drug discovery

There has been an explosion of studies of animal models of asthma in the past 20 years. The elucidation of fundamental immunological mechanisms underlying the development of allergy and the complex cytokine and chemokines networks underlying the responses have been substantially unraveled. Translation of findings to human asthma have been slow and hindered by the varied phenotypes that human asthma represents. New areas for expansion of modeling include virally mediated airway inflammation, oxidant stress, and the interactions of stimuli triggering innate immune and adaptive immune responses.

The effects of antisense interleukin-4 gene transferred by recombinant adeno-associated virus vector on the airway remodeling in allergic rats

BACKGROUND

Th2-derived cytokines, including interleukin-4 (IL-4), are considered to play an important role in the development of airway remodeling of asthma.

OBJECTIVES

Our previous study has demonstrated that a recombinant adeno-associated virus containing antisense against IL-4 gene (rAAV-asIL4) vector could significantly suppress the expression of IL-4 protein and airway inflammation in the rat models of allergic asthma. In this study, we applied the rAAV-asIL4 vector to allergic rats to investigate the effects of anti-IL4 therapy on airway remodeling in allergic asthma.

METHODS

rAAV-asIL4 was used to infect the ovalbumin (OVA)-sensitized and challenged rats by tail-vein injection. IL-4 protein in bronchoalveolar lavage fluid (BALF) was detected by enzyme-linked immunosorbent assay. The number of eosinophils in BALF was counted. Transforming growth factor-beta1 (TGF-beta1) and TGF-beta2-positive cells in the peribronchial space were detected by immunohistochemical staining, and collagen deposition beneath the basement membrane was detected by Sirius red stain. The lung tissues were collected for histologic analysis of total bronchial wall area (W(At)) and airway smooth muscle area (W(Am)).

RESULTS

rAAV-asIL4 significantly decreased IL-4 protein in BALF of OVA-sensitized and challenged rats. The number of eosinophils in BALF, the TGF-beta1 and TGF-beta2-positive cells in the peribronchial space were also suppressed. Moreover, the rAAV-asIL4 treatment inhibited the area of Sirius red staining in airways and the increase in W(At) and W(Am).

CONCLUSION

These results suggest that rAAV-asIL4 may attenuate the airway remodeling process relevant to the inhibition of airway inflammation. This study provides elementary evidence for the potential utility of rAAV-asIL4 as an approach to gene therapy for asthmatic airway remodeling.

Effects of antisense interleukin-5 gene transferred by recombinant adeno-associated virus to allergic rats

BACKGROUND AND OBJECTIVE

The accumulation of eosinophils in airways is an important characteristic of asthma. The process is primarily mediated by interleukin-5 (IL-5) secreted by Th2 lymphocytes. This study explored a new approach to asthma therapy in which allergic rats were transfected with the IL-5 antisense gene delivered by the recombinant adeno-associated virus (rAAV-ASIL-5).

METHODS

The viral vector rAAV-ASIL-5 was constructed and the IL-5 antisense gene transfected into allergic rats. The levels of IL-5, IgE, eotaxin and eosinophilic cationic protein (ECP) in sera and bronchoalveolar lavage fluid (BALF) were measured by ELISA. The inflammatory responses in lung tissues were evaluated by histological study.

RESULTS

The levels of IL-5 protein in serum and BALF were significantly decreased in the allergic rats treated with rAAV-ASIL-5 (P < 0.05). Serum ovalbumin-specific IgE was reduced in treated rats compared with untreated rats (P < 0.05). rAAV-ASIL-5 treatment also reduced eosinophils in the peripheral blood and BALF, as well as the ECP and eotaxin levels in serum and BALF (P < 0.05). There was significantly less inflammation in the lungs of rAAV-ASIL-5-treated rats than in those of untreated rats. No obvious pathological damage to the kidneys and livers of the rats treated with rAAV was observed.

CONCLUSIONS

Treatment with rAAV-ASIL-5 inhibited the accumulation of eosinophils and airway inflammation in the rat model of allergic asthma by suppressing IL-5 production. These results suggest that rAAV-ASIL-5-based gene therapy may be used for the treatment of allergic asthma.

Enhanced deposition of low-molecular-weight hyaluronan in lungs of cigarette smoke-exposed mice

Chronic obstructive pulmonary disease (COPD) is characterized by infiltration of inflammatory cells, destruction of lung parenchyma, and airway wall remodeling. Hyaluronan (HA) is a component of the extracellular matrix, and low-molecular-weight (LMW) HA fragments have proinflammatory capacities. We evaluated the presence of HA in alveolar and airway walls of C57BL/6 mice that were exposed to air or cigarette smoke (CS) for 4 weeks (subacute) or 24 weeks (chronic). We measured deposition of the extracellular matrix proteins collagen and fibronectin in airway walls and determined the molecular weight of HA purified from lung tissue. In addition, we studied the expression of HA-modulating genes by RT-PCR. HA staining in alveolar walls was significantly enhanced upon chronic CS exposure, whereas HA levels in the airway walls were already significantly higher upon subacute CS exposure and remained elevated upon chronic CS exposure. This differed from the deposition of collagen and fibronectin, which are only elevated at the chronic time point. In lungs of CS-exposed mice, the molecular weight of HA clearly shifted toward more LMW HA fragments. CS exposure significantly increased the mRNA expression of the HA synthase gene Has3 in total lung tissue, whereas the expression of Has1 was decreased. These in vivo studies in an experimental model of COPD show that CS exposure leads to enhanced deposition of (mostly LMW) HA in alveolar and bronchial walls by altering the expression of HA-modulating enzymes. This may contribute to airway wall remodeling and pulmonary inflammation in COPD.

Inverse relationship between Sec14l3 mRNA/protein expression and allergic airway inflammation

Bronchial asthma is an inflammatory disease of the airways. The Sec14l3 gene, encoding a 45-kDa secretory protein, is specifically expressed in airway epithelium. Here, we report on the kinetics of Sec14l3 expression following allergic inflammation of the lung. Brown Norway rats were sensitized by intraperitoneal injection of ovalbumin, followed by challenge with aerosolized ovalbumin after a 3-week interval. This animal model showed many features similar to human allergic asthma: an increase in inflammatory cells such as eosinophils, lymphocytes and neutrophils in bronchoalveolar lavage (BAL) fluid and histopathological alteration of lung tissue, exhibiting infiltration of these inflammatory cells and degeneration and necrosis of alveolar epithelium. These parameters reached their maximal level 24h after allergen challenge. In contrast, quantitative polymerase chain reaction analyses demonstrated a rapid and significant reduction of Sec14l3 mRNA in lung tissue and maximum reduction (to 1.4% of the control) was observed at 24h. Pretreatment with dexamethasone significantly suppressed both the Sec14I3 mRNA reduction and all of the inflammatory changes. The 45-kDa secretory protein was identified in the supernatant of BAL fluids. Two-dimensional gel images of the supernatant proteome also revealed down-regulation of the protein following inflammation (to approximately 30% of the control at 24h). Thus, Sec14l3 expression is highly and inversely associated with the progression of airway inflammation. Sec14l3 mRNA and protein may function in the homeostasis of airway epithelial cells under normal conditions.

Chronic intranasal administration of Aspergillus fumigatus spores leads to aggravation of airway inflammation and remodelling in asthmatic rats

BACKGROUND AND OBJECTIVE

Epidemiological evidence indicates a close link between exposure to fungi and deterioration of asthma. However, the role of fungi as an exogenous precipitant for initiation and progression of asthma has been incompletely explored. In this study, the effects of Aspergillus fumigatus exposure on airway inflammation and remodelling in a rat model of chronic asthma were investigated.

METHODS

The rat model of chronic asthma was established by systemic sensitization and repeated challenge with ovalbumin (OVA). The asthmatic rats were exposed to chronic intranasal inhalation of A. fumigatus spores. Changes in airway inflammation, remodelling and BHR were measured after exposure to the fungus.

RESULTS

Chronic inhalation of A. fumigatus spores elevated the production of T helper 2 (Th2) cytokines, increased the concentration of total serum IgE, and resulted in the recruitment of eosinophils and lymphocyte infiltration into the airways of asthmatic rats. Goblet cell hyperplasia, mucus hyperproduction and subepithelial collagen deposition were also induced by inhalation of the fungus. The remodelling changes induced by inhalation of the fungus paralleled the changes in BHR in this rat model of asthma.

CONCLUSIONS

Chronic exposure to A. fumigatus aggravated Th2 airway inflammation, promoted airway remodelling and increased BHR in OVA-sensitized and -challenged rats.

Structural aspects of airway remodeling in asthma

Airway remodeling in asthma is a complex process that involves structural changes in virtually all tissues of the airway wall. The histologic changes to the airways consist of epithelial proliferation and goblet cell differentiation, subepithelial fibrosis, airway smooth muscle (ASM) growth, angiogenesis, matrix protein deposition, gland hyperplasia and hypertrophy, and nerve proliferation. Cytokines, chemokines, and growth factors from inflammatory cells and structural cells contribute to remodeling. There are complex interactions among the various signaling pathways involving matrix metalloproteinases that are required for growth factor release. The physiologic consequences of remodeling are airway hyperresponsiveness from ASM growth and mucus hypersecretion from gland and goblet cell hyperplasia. Airway stiffening is a probable contributor to airway hyperresponsiveness through attenuation of the transmission of potently bronchodilating cyclical stress to the ASM during breathing. The epidermal growth factor receptor's role in remodeling and its interaction with other potential causes of remodeling are discussed.